‘We want to believe you,’ said Stephanopoulos, playing the role of most unlikely ‘good cop’ in the history of policing. I made myself pause and take a deep breath. I hadn’t done any advanced interview courses but I knew the basics, and the conduct of this interview was far too sloppy. I looked at Seawoll and he gave me the ‘at last he wakes up’ look so beloved of teachers, senior detectives and upper-middle-class mothers.

‘What do you want to believe?’ I asked.

‘That magic is real,’ Seawoll said, and gave me a knowing smile. ‘Can you give us a demonstration?’

‘That’s not a good idea,’ I said. ‘There could be side effects.’

‘Sounds a bit too convenient to me,’ said Stephanopoulos. ‘What kind of side effects?’

‘Probably destroy your mobile phones, palm pilot, laptop or any other electronic equipment in the room,’ I said.

‘What about the tape recorder?’ asked Seawoll.

‘That too,’ I said.

‘And the CCTV?’

‘Same as the tape recorder,’ I said. ‘You can protect the phones by disconnecting them from their batteries.’

‘I don’t believe you,’ said Stephanopoulos, and leaned forward aggressively, neatly masking from the camera behind her the fact that she was popping the battery from her very ladylike Nokia slimline.

‘I think we’re going to want a demonstration,’ said Seawoll.

‘How much of a demonstration?’ I asked.

‘Show us what you’re made of, son,’ said Seawoll.

It had been a really long day and I was knackered, so I went for the one forma I can reliably do in a crisis – I made a werelight. It was pale and insubstantial under the fluorescent strip lighting and Seawoll wasn’t impressed, but Stephanopoulos’s heavy face broke into such a wide smile of unalloyed delight that for a moment I saw her as a young girl in a pink room full of stuffed unicorns. ‘It’s beautiful,’ she said.

One of the tapes unspooled messily inside the tape machine while the other just stopped dead. I knew from my experiments that I needed to up the strength of the werelight to take out the camera. I was going for a brighter light when the ‘shape’ in my mind went wrong and suddenly I had a column of light hitting the ceiling. It was a bright blue colour, and focused. When I moved my hand the beam played across the walls – it was like having my own personal searchlight.

‘I was hoping for something a bit more subtle,’ said Seawoll.

I shut the light down and tried to remember the ‘shape’, but it was like trying to remember a dream, slipping away even as I grabbed for it. I knew I was going to have to spend a long time in the lab trying to recapture that form, but as Nightingale had said right at the beginning, knowing the forma is there is half the battle.